This invention relates to air cushion vehicles wherein powered fans provide vertical lift and horizontal propulsion, it being a general object to provide a maneuverable vehicle of substantial size adaptable to a multitude of practical purposes. The concept herein disclosed provides a vehicle adapted to operate over land, water, ice, mud, marsh, agricultural crops, or any combination thereof, and over many surfaces that would restrict or preclude the movement of more conventional vehicles. Primarily with vehicles of the type under consideration, it is obstacles and interruptions and/or grades and undulations in the earths surface which are to be encountered and successfully traversed. And it is a matter of economics that such a vehicle be acceptable with respect to fuel consumption as related to both speed and load capabilities, and it is here that the vehicle of the present invention compares most favorably with conventional aircraft, helicopters and hovercraft and the like. For example, the air cushion vehicle herein disclosed having a true cargo capability of 5,000 lbs. uses 25 gals. of fuel per hour with a total direct operating cost of $53 per hour; as compared with a British Hovercraft known as the SR N6 having a true cargo capability of 4,400 lbs. that uses 88 gals. of fuel per hour with a total direct operating cost of $227 per hour; or as compared with a Sikorski helicopter known as the S-58T having a true cargo capability of 3,170 lbs. that uses 110 gals. of fuel per hour with a total direct operating cost of $368 per hour; as compared with a Sikorski helicopter known as the S-61N having a true cargo capability of 3,785 lbs. that uses 160 gals. of fuel per hour with a total direct operating cost of $643 per hour; or as compared with the Bell Aero Space air cushion vehicle known as the Viking having a true cargo capability of 6,500 lbs. that uses 90 gals. of fuel per hour with a total operating cost of $205. Notice that the fuel consumption and operating cost per hour is far less with the air cushion vehicles as compared with helicopters, and that these operating figures are far less with the concept herein disclosed as compared with the closest related (British Hovercraft and Bell Aero) prior art. Additionally, the said total direct operating cost referred to herein considers the factors of initial cost, range with cargo, hourly operating cost, hourly maintenance cost, and hourly depreciation cost. Generally therefore, it is an improved air cushion vehicle that is hereinafter disclosed and claimed.
The air cushion vehicle herein disclosed is essentially of "lighter" configuration, a substantially large flat bottomed barge with useful open deck space. That is, it is a work machine unencumbered by the conventional limitations of wheels or tracks, or by rotor blades, or by hull draft when used over water. Characteristically, this vehicle comprises a virtually unsinkable monocoque hull fabricated over a space frame with a durable shell filled with cellular foam plastic for strength and flotation; i.e. 200% displacement of its gross weight in sea water. In practice, aluminum tubing and sheet combined with resin bonded fiberglass is employed in the construction, it being an object to provide a relatively light weight structure for its size, and of durable construction that will remain sound and operable under the most adverse circumstances.
The air cushion vehicle herein disclosed is characterized by a lift plenum bordered by a seal or skirt that is flexible so as to move over irregularities of the terrain or water surface and/or any combination thereof which may be encountered. Low pressure air, for example at 35 lbs. per square foot (1/4 lb. per square inch) is dynamically supplied to the lift plenum and permitted to discharge from beneath the skirt that is juxtaposed to the supporting surface. It is an object herein to provide a versatile and extremely wear resistant peripheral skirt system that is adapted to encounter and surmount obstacles such as steps and undulations in the supporting surface, and voids therein as well such as ditches and the like. With the skirt system hereinafter disclosed, there is an inflated perimeter wall of woven fiber and plastic, unaffected by climatic changes and serviceable by means of its zippered or lapped together panel sections which facilitate rapid installation, inspection and replacement for repair. In practice, the skirt is comprised of interconnected tubes that are of substantial cross section and adapted to be depressed by obstacles as variations in the supporting surface are encountered. The escape of plenum air is via an air gap that averages 1/2 inch beneath the skirt.
It is an object of this invention to provide increased stability in an air cushion vehicle of the type under consideration, namely roll control whereby the desired air gap beneath the skirt is maintained. With the present invention there is a roll stabilizer divider that symmetrically separates the plenum into right and left chambers for receiving lift air from an axial flow lift fan. The said fan supplies sufficient excess cushion capacity for crossing ditches and for overcoming lop-sided obstacles.
It is also an object of this invention to provide an air cushion vehicle having the features thus far described and which can be diminished in size for transport, without dismantling. That is, the vehicle components remain integrally attached and are moveable into working positions while augmenting the vehicle to its operable configuration and full size. With the present invention, highway mobility is provided in the diminished configuration, with the attachment of and/or lowering of a wheeled support, together with inward folding of the opposite side margins of the hull and with rotation of the propulsion unit from a beam-to-beam into a fore-and-aft disposition. The purpose of said folding and rotation of elements is to narrow the structure so as to be within the width limits for conventional highway transport. With this invention, the opposite sides of the hull comprise sponsons hingedly attached thereto to extend coextensive with the hull respectively, and the propulsion unit comprises a turret-like bridge that overlies the hull and sponsons when disposed transversely and which is confined to overlie the hull when disposed longitudinally. In practice, the propulsion unit is located aft on the hull, while the lift fan unit is located forward in the hull with an adjoining pilot house facing forwardly therefrom.
It is still another object of this invention to provide for directional control and maneuverability. The propulsion unit is composed of engine driven propeller means, preferably right and left reversible and variable speed propellers on substantially spaced axes. Moderate and high speed turning is accomplished with a cascade of vanes (rudders) in the propeller driven slip-stream, and which is amplified by asymmetrical throttle control. Directional stability is precisely controlled by means of castering tracking gears and an extensible steering nose wheel. The tracking gears trail with a downward pressure to support a portion of the vehicle weight, say for example 10%-20% thereof, and they can be raised and lowered independently or operated in conjunction with the nose wheel. And, the nose wheel is also retractable. Thus for example, precise directional control can be utilized for furrow following in agricultural operations, similar to a water keel effect which is also provided by the longitudinally disposed skirts and center roll stability divider.
A feature of the air cushion vehicle herein disclosed is its ability to successfully encounter substantial irregularities in rolling terrain and water swells, all by virtue of the large diameter skirt tubes and placement of the hull bottom over said tubes. Therefore, and much like aircraft in close ground proximity, there is a ground effect with the dynamic escape of lift air which tends to maintain a uniform separation between the depressible skirts and the terrain or water surface. For example, with a skirt of 24 inch diameter, a 20 inch boulder will pass beneath without notice. However, such an obstacle more than 24 inches high will of course come into contact with the hull and impair progress. Still further, climbing capability is within the operation of this air cushion vehicle, and for example in the embodiment described herein is capable of ascending a 20%-22% grade, and steeper slopes dependent upon approach speed and grade transition. While this air cushion vehicle is capable of relatively high over the surface speeds, work capabilities have dominated the concept so that commercial operation thereof is in the 20-40 m.p.h. range, while top speed is in the 50-100 m.p.h. range. In practice, three 200 horse power aircraft type reciprocating gasoline engines, one for the lift unit and two for the propulsion unit are employed.
Finally, it is an object to transport this air cushion vehicle over highways in its diminished configuration, and to this end a tow bar is attached thereto and hitched to a fifth wheel support of a tractor vehicle or truck as shown in the drawings.